Đặt \(A=\left|x-2002\right|+\left|x-2001\right|\)
\(A=\left|x-2002\right|+\left|2001-x\right|\ge\left|x-2002+2001-x\right|=\left|-1\right|=1\)
Dấu "=" xảy ra \(\Leftrightarrow\left(x-2002\right)\left(2001-x\right)\ge0\Leftrightarrow2001\le x\le2002\)
Đặt A=|x−2002|+|x−2001|
\(\Rightarrow\)A=|x−2002|+|2001−x| ≥ |x−2002+2001−x| = |−1| =1
Dấu "=" xảy ra ⇔(x−2002)(2001−x) ≥ 0 ⇔ 2001 ≤ x ≤ 2002
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